Laser optical instruments employing a laser beam include a laser beam machining device, a laser beam measuring device, etc., for example. Such laser optical instruments incorporate various optical components such as lenses, reflecting mirrors, etc. for guiding a laser beam to a predetermined applying position. Reflecting mirrors are available in various types including a plane mirror, a parabolic mirror, and an elliptical mirror.
When assembling laser optical instruments, therefore, it is desirable to make alignment adjustments accurately for layout adjustments, focal point measurements, etc. of various optical components in order to reliably perform high-quality laser machining processes and highly accurate laser measuring processes.
Generally, He—Ne laser is used to make such alignment adjustments. Specifically, a laser beam emitted from an He—Ne laser source is used as a reference beam for layout adjustments, focal point measurements, etc. of optical components. However, the laser beam emitted from an He—Ne laser source is problematic in that the absolute position of the laser beam cannot easily be obtained because there is no center (optical center) in the laser beam.
Laser beams do not have a definite configuration as they oscillate in longitudinal modes or transverse modes depending on the oscillator structure. Furthermore, a laser beam needs to be large in diameter in order to achieve desired parallelism between the laser beam and a mechanical axis. It has been pointed out that it is not possible to reliably obtain a sufficiently thin, parallel, and straight laser beam that is required as a reference beam.
In order to make accurate alignment adjustments of optical components, it is necessary to detect a sole accurate reflecting optical axis aligned with a mechanism axis. However, it is considerably difficult to accurately detect such a reflecting optical axis. As a result, it has been impossible to make highly accurate alignment adjustments of optical components.
It has been customary to measure the focal point of a focusing optical system such as a parabolic mirror, an elliptical mirror, or the like by actually applying reflected light from the focusing optical system to a wall or the like and directly observing how the applied light is focused.
However, the focal point of the focusing optical system varies depending on the parallelism of the light applied thereto, the layout of the focusing optical system, the surface accuracy thereof, and other elements, making it difficult to achieve a desired reproducibility of measurements. Consequently, the focal point of the focusing optical system cannot accurately be measured.
Laser optical instruments have a plurality of optical components mounted on an optical tabletop in alignment with the optical axis of a laser beam. Since it is difficult to make alignment adjustments of the optical components on the optical tabletop, the process of making alignment adjustments is highly complex and such alignment adjustments cannot be made with accuracy.
One solution is to make alignment adjustments of the optical components before the optical components are installed on the optical tabletop. However, even if the alignment adjustments of the optical components have been made accurately, the optical components may possibly be brought out of alignment with the optical axis due to assembling errors and mechanical errors. For this reason, highly accurate alignment adjustments of the optical components have not been possible in the art.